Fangjun Jiang has pointed you to the function lists in the documentation. As another approach, I recommend contacting the MathWorks Sales department using the telephone icon in the upper-right corner of this page. If you describe to the Sales staff the work that you want to perform using MathWorks products at a high level they can recommend which products may be useful for that work and why you may find those products useful.
Alternately you could find the general application area in which you're working (since you mention root locus, I'm guessing you're working on designing and developing control systems) on this page. On the Control Systems page there are descriptions of some topics in that field that you could use MathWorks products for and each has videos, suggested products, and/or user stories that provide more information on how you could use MathWorks products for that topic. That might be a good first step to do before talking to Sales as that could provide a focus for your conversation with the Sales staff.
Alternately, you could search mathworks.com for the phrase "root locus". The first two hits are to a topic discovery page that mentions Control System Toolbox and a topic page in the documentation for Control System Toolbox.
